Additive manufacturing apparatus

ABSTRACT

An additive manufacturing apparatus includes a chamber, a material layer former, an inert gas supplier, and a material supply unit. The material supply unit includes a material tank, a transporter, and a sieve. The material tank stores material. The transporter transports the material discharged from the chamber and the material tank to the highest level of a conveyance route of the material. The sieve is provided below the transporter and above the chamber, removes impurities from the material sent from the transporter and then discharge the material downward to replenish the material layer former with the material.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Japanese Application Serial No. 2020-175925, filed on Oct. 20, 2020, and Japanese Application Serial No. 2020-207386, filed on Dec. 15, 2020. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND Technical Field

The disclosure relates to an additive manufacturing apparatus.

Description of Related Art

Various methods are known as additive manufacturing methods for three-dimensional molded objects. For example, an additive manufacturing apparatus that implements powder bed fusion forms a material layer by leveling powder material in a chamber and irradiates the material layer with a laser beam or an electron beam to sinter or melt the material, and thereby forms a solidified layer. The formation of a material layer and a solidified layer is repeated to laminate a plurality of solidified layers, and thereby a desired three-dimensional molded object is produced. Further, during or after molding, the solidified layer(s) may be subjected to cutting within the additive manufacturing apparatus.

All material supplied in a chamber is not solidified, and thus unsolidified excess material is accumulated in the chamber. It is desirable to collect and reuse the excess material in order to reduce costs for molding. On the other hand, impurities such as spatters scattering when the solidified layer is formed or cutting chips generated during cutting can be incorporated into the excess material in the chamber, and thus it is not preferred to reuse the material as it is.

U.S. Patent Application Publication US2017/0348771A1 discloses an additive manufacturing apparatus that reuse excess material after the material is collected from a chamber and sieved to remove impurities. More specifically, excess material discharged from the chamber is conveyed by a material collecting conveyance device, fed to an impurity removal device that is a sieving device from above, and thereby impurities are removed. Then, the excess material discharged downward from the impurity removal device is sent to a material replenishing unit provided at an upper part of the chamber by a material supply conveyance device, and appropriately re-supplied to a recoater head.

A conventional additive manufacturing apparatus that collects excess material from a chamber, removes impurities using a sieve, and reuses the material needs a first transporter that sends excess material to above the sieve and a second transporter that sends the excess material from the sieve to above the chamber. For that reason, costs for the devices are high and maintenance such as cleaning in the event of change of material is relatively laborious.

SUMMARY

According to an embodiment of the disclosure, an additive manufacturing apparatus including a chamber, a material layer former provided in the chamber and configured to form a material layer with a predetermined thickness, an inert gas supplier configured to supply an inert gas at a predetermined concentration to the chamber, and a material supply unit configured to collect material discharged from the chamber and replenish the material layer former with the material is provided, in which the material supply unit includes a material tank configured to store the material, a transporter configured to transport the material discharged from the chamber and the material tank to a highest level on a conveyance route of the material, and a sieve provided below the transporter and above the chamber, and configured to remove impurities from the material sent from the transporter and discharge the material downward to replenish the material layer former with the material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of an additive manufacturing apparatus.

FIG. 2 is a schematic configuration view of an additive manufacturing apparatus body.

FIG. 3 is a perspective view taken from above a recoater head.

FIG. 4 is a perspective view taken from below the recoater head.

FIG. 5 is a schematic configuration view of an irradiation device.

FIG. 6 is a perspective view of a material supply unit.

FIG. 7 is a schematic configuration view of the material supply unit.

FIG. 8 is a side view of a transporter.

FIG. 9 is a cross-sectional view of the transporter.

FIG. 10 is a perspective view of a sieve and a connecting member.

FIG. 11 is a cross-sectional view of the sieve and the connecting member.

FIG. 12 is a perspective view of the connecting member, a guide member, and the recoater head.

FIG. 13 is a cross-sectional view of the connecting member, the guide member, and the recoater head.

FIG. 14 is a vicinity view of the guide member taken from a side of a chamber.

FIG. 15 is a perspective view of the guide member.

FIG. 16 is a cross-sectional part of the guide member when material is being discharged.

FIG. 17 is a cross-sectional part of the guide member when material is not being discharged.

FIG. 18 is a flowchart showing an example of a material replenishing operation during additive manufacturing.

FIG. 19 is a flowchart showing an example of a material collecting operation after additive manufacturing.

DESCRIPTION OF THE EMBODIMENTS

The disclosure has been conceived in view of the above circumstances and provides an additive manufacturing apparatus that can collect and replenish material with a simpler configuration.

In the additive manufacturing apparatus according to the disclosure, a sieve is disposed above the chamber, and a transporter transports material to the highest level of a material conveyance route. Because material can be transported with one transporter, the cost of the apparatus can be reduced, and the apparatus can have a relatively simpler configuration.

An embodiment of the disclosure will be described using the drawings. Various modified examples described below may be implemented by optionally combining with the others. Further, hoses, pipes, and the like may be appropriately omitted in the drawings.

An additive manufacturing apparatus 1 according to the present embodiment includes an additive manufacturing apparatus body 10, an inert gas supplier 21, a fume collector 23, and a material supply unit 5 as illustrated in FIGS. 1 and 2.

The additive manufacturing apparatus body 10 performs additive manufacturing, specifically, powder bed fusion. In this specification, additive manufacturing is also referred to as molding. The additive manufacturing apparatus body 10 repeats formation of a material layer 83 and a solidified layer 85 to manufacture a desired three-dimensional molded object. The material layer 83 and the solidified layer 85 are formed for each divided layer, which is obtained by dividing data of the three-dimensional molded object at a predetermined thickness. The additive manufacturing apparatus body 10 includes a chamber 11, a guide member 37, a material layer former 3, an irradiation device 4, and a controller 7.

The chamber 11 is configured to be virtually sealed, and covers a molding region R that is a region in which the desired three-dimensional molded object is formed. The inside of the chamber 11 is filled with an inert gas at a predetermined concentration.

The material layer former 3 is provided inside the chamber 11 and forms a material layer 83 with a predetermined thickness. The material layer former 3 includes a base 31 including the molding region R and a recoater head 33 disposed on the base 31 and configured to be movable in a horizontal direction. A molding table 14 is disposed in the molding region R, and the molding table 14 is configured to be moved by a molding table driver 15 in a vertical direction. At the time of molding, a base plate 81 is disposed on the molding table 14, and a first material layer 83 is formed on the base plate 81.

A pair of discharge openings 311 and 313 are formed in the base 31 with the molding region R interposed therebetween, and a first discharge chute 16 and a second discharge chute 17 are provided below the discharge openings 311 and 313, respectively. Excess material fed from the discharge openings 311 and 313 is first retained in each of the first discharge chute 16 and the second discharge chute 17.

The recoater head 33 includes a material container 331, a material supply port 333, and a material discharge port 335 as illustrated in FIGS. 3 and 4. The material container 331 stores material. In the present embodiment, the material is, for example, a metal powder. The material supply port 333 is provided on an upper surface of the material container 331 and functions as a receiving port for material supplied to the material container 331. The material sent from the material supply unit 5 is fed to the material supply port 333 via the guide member 37. The material discharge port 335 is provided at a bottom of the material container 331 and discharges the material retained inside the material container 331. The material discharge port 335 has a slit shape extending in a horizontal direction orthogonal to the movement direction of the recoater head 33. A pair of blades 35 that levels the material to form the material layer 83 is provided on the sides of the recoater head 33. The recoater head 33 moves back and forth in the horizontal direction on the molding region R while discharging the material contained in the material container 331 from the material discharge port 335. At that moment, the blades 35 flatten the discharged material to form the material layer 83. The material layer 83 is made of the powder material.

Further, the excess material spread on the base 31 is extruded by the blades 35 as the recoater head 33 moves and discharged from the discharge openings 311 and 313. In addition, when it is desired to empty the inside of the material container 331 of the material, the recoater head 33 is moved over the discharge openings 311 and 313.

A suction nozzle 18 that can suction the material is disposed inside the chamber 11. In the present embodiment, a glove box, which is not illustrated, is provided in the chamber 11, and an operator can move the suction nozzle 18 to any place inside the chamber 11 through the glove box. The suction nozzle 18 enables the excess material inside the chamber 11 to be collected outside of the chamber 11. Mostly, unsolidified material on the molding table 14 or the base 31 is collected by the suction nozzle 18.

The chamber 11 includes a molding chamber 11 a in which the molding region R is positioned and additive manufacturing is performed, and a replenish chamber 11 c in which the guide member 37 is disposed and the material is supplied from the guide member 37 to the recoater head 33. The molding chamber 11 a communicates with the replenish chamber 11 c, and the recoater head 33 can reciprocate between the molding chamber 11 a and the replenish chamber 11 c.

The irradiation device 4 is provided above the chamber 11. The irradiation device 4 irradiates a predetermined irradiation region of the material layer 83 formed on the molding region R with a laser beam L to melt or sinter the material layer 83 at an irradiation position, and thereby the solidified layer 85 is formed. The irradiation region is present within the molding region R and approximately matches a region surrounded by the contour shape of the three-dimensional molded object for a predetermined divided layer. The irradiation device 4 includes a beam source 41, a collimator 43, a focus control unit 45, and a galvano scanner 47 as illustrated in FIG. 5.

The beam source 41 generates the laser beam L. Here, a type of the laser beam L is not limited as long as it can sinter or melt the material layer 83, and for example, the laser beam L is a fiber laser, a CO₂ laser, a YAG laser, a green laser, or a blue laser. The collimator 43 converts the laser beam L output by the beam source 41 into parallel light. The focus control unit 45 has a condensing lens and a motor that moves the condensing lens back and forth to adjust the laser beam L output by the beam source 41 to a desired spot diameter. The galvano scanner 47 is a scanner to scan the laser beam L, and includes a pair of galvano mirrors 47 x and 47 y and actuators each of which rotates the galvano mirrors 47 x and 47 y. The galvano mirrors 47 x and 47 y are controlled such that their rotation angles change according to a magnitude of a rotation angle control signal input from the controller 7 to two-dimensionally scan the laser beam L output from the beam source 41.

The laser beam L that has passed through the galvano mirrors 47 x and 47 y is transmitted through a window 12 provided in a top plate 11 b of the molding chamber 11 a and irradiates the material layer 83 formed in the molding region R. The window 12 is formed of material that can transmit the laser beam L. In a case in which the laser beam L is the fiber laser or the YAG laser, for example, the window 12 may be formed of quartz glass.

A contamination prevention device 13 is provided at the top plate 11 b of the molding chamber 11 a to cover the window 12. The contamination prevention device 13 prevents fumes generated during the formation of the solidified layer 85 from adhering to the window 12. The contamination prevention device 13 includes a cylindrical housing and a cylindrical diffusion member disposed within the housing. An inert gas supply space is provided between the housing and the diffusion member. In addition, an opening is provided at a bottom of the housing on an inner side of the diffusion member. Many pores are provided in the diffusion member, and clean inert gas supplied in the inert gas supply space passes through the pores to fill the clean chamber. Then, the clean inert gas filling the clean chamber is ejected downward from the contamination prevention device 13 through the opening. In this manner, the fumes are prevented from adhering to the window 12.

Further, the irradiation device may irradiate the material layer 83 with, for example, an electron beam to sinter or melt the layer to form the solidified layer 85. The irradiation device may include, for example, a cathode electrode that discharges electrons, an anode electrode that causes electrons to converge and accelerates them, a solenoid that forms a magnetic field to cause directions of the electron beam to converge to one direction, and a collector electrode that is electrically connected the material layer 83 that is an irradiation target. A voltage is applied between the collector electrode and the cathode electrode. In this variation, the cathode electrode and the cathode electrode serve as a beam source to generate the electron beam, and the solenoid serves as a scanner to scan the electron beam. That is, any device including a beam source that generates the laser beam L or the electron beam, and a scanner that scans the laser beam L or the electron beam may be used as the irradiation device.

The controller 7 controls the molding table 14, the material layer former 3 and the irradiation device 4 of the additive manufacturing apparatus body 10, the inert gas supplier 21, the fume collector 23, and the material supply unit 5. The controller 7 includes an arithmetic processor, a memory, a storage, an input device 71 that receives input from a keyboard, a touch panel, or the like and reads an external storage medium, and a display device 73 that displays operation screens and various parameters.

The additive manufacturing apparatus body 10 may include a cutting device with a rotating cutting tool such as an end mill and a shaping tool such as a tool bit. The cutting device may cut solidified layers 85 each time a predetermined number of solidified layers 85 are formed. In addition, the cutting device may cut and remove a protrusion created by a sputter adhering on an upper surface of the solidified layer 85. In addition, the cutting device may cut the solidified layers 85 to form reference surfaces for secondary processing after the additive manufacturing is completed.

The inert gas supplier 21 supplies the inert gas at the predetermined concentration to the chamber 11. The inert gas supplier 21 is, for example, an inert gas generator that generates the inert gas from the air or a gas cylinder that stores the inert gas. In the present embodiment, the inert gas supplier 21 is, for example, a PSA-type nitrogen generator or a membrane separation-type nitrogen generator. Preferably, the inert gas supplier 21 supplies an inert gas to the material supply unit 5 as well as the chamber 11. In addition, preferably, the inert gas supplier 21 is capable of switching a supply amount of the inert gas. Further, in the disclosure, the inert gas is a gas that does not substantially react with the material layer 83 and the solidified layer 85, and an appropriate gas among nitrogen gas, argon gas, helium gas, and the like is selected according to the type of the material.

The fume collector 23 removes the fumes from the inert gas discharged from the chamber 11 and returns the fumes to the chamber 11. The fume collector 23 is, for example, an electrostatic precipitator or a filter.

The material supply unit 5 collects the material discharged from the chamber 11 and replenishes the material layer former 3 with the material. The material supply unit 5 includes a cabinet 51, a material tank 52, a transporter 53, a first switching valve 54, a sieve 55, a second switching valve 56, and a connection member 57, as illustrated in FIGS. 6 and 7. Further, in FIG. 7, flows of the material are represented by solid-line arrows, and flows of gases are represented by dashed-line arrows. In addition, although not illustrated in FIG. 7, each part of the material supply unit 5 is electrically connected to the controller 7 via a connector 631.

In a case in which a plurality of types of material is used as material of the additive manufacturing apparatus 1, it is desirable to provide material supply units 5 for each of the material and switch between the material supply units 5 for each type of material. With this configuration, cleaning resulting from the switching of the material need only be performed on the additive manufacturing apparatus body 10, and thus change of the material can be made with no effort in a relatively short period of time.

The cabinet 51 can be moved by casters 511, and houses the material tank 52, the transporter 53, the first switching valve 54, the sieve 55, the second switching valve 56, and the connection member 57.

The material tank 52 stores the material to be used in additive manufacturing. When the material tank 52 is to be replenished with the material, for example, a material bottle 521 retaining the material is connected to the material tank 52 to perform replenishment of the material. The material bottle 521 is provided with an opening/closing valve 521 a, and thus replenishment of the material can be performed by opening the opening/closing valve 521 a after the connection to the material tank 52, without exposing the material. The material tank 52 and the transporter 53 are connected via a valve 641 that may be a butterfly valve.

Further, in order to prevent degradation of the material, it is desirable to fill a conveyance route of the material in the material supply unit 5 with the inert gas. In the present embodiment, the inert gas supplier 21 is also connected to the material tank 52 via a coupler 621 to supply the inert gas to the material tank 52 as well as the chamber 11. In addition, it is desirable to provide a first bypass 651 connected to the chamber 11 and the material tank 52 via a coupler 622, and a second bypass 652 connected to the material tank 52 and a pipe disposed between the material tank 52 and the transporter 53. The first bypass 651 and the second bypass 652 are pipelines in which an inert gas can flow. According to the above configuration, the chamber 11, the material tank 52, and the pipe between the material tank 52 and the transporter 53 have an equal pressure, and thus material can be favorably transported.

The transporter 53 transports the material discharged from the chamber 11 and the material tank 52 to the highest level of the conveyance route of the material. The transporter 53 includes, for example, a vacuum conveyor 531 and an ejector 533 as illustrated in FIGS. 8 and 9. A pair of the first discharge chute 16 and the transporter 53, a pair of the second discharge chute 17 and the transporter 53, and a pair of the suction nozzle 18 and the transporter 53 are respectively connected via, for example, ferrules 611, 612, and 613, and valves 642, 643, and 644 that are, for example, butterfly valves.

The vacuum conveyor 531 includes a sealed vacuum container 531 a. A supply pipe 531 b and an exhaust pipe 531 c are provided at an upper part of the vacuum container 531 a, and a discharge port 531 e is formed at a lower end of the vacuum container 531 a. The supply pipe 531 b is connected to the chamber 11 and the material tank 52. More specifically, the supply pipe 531 b is connected to the material tank 52, the first discharge chute 16, the second discharge chute 17, and the suction nozzle 18, and suctions up the material using negative pressure generated in the vacuum container 531 a and sends the material to the vacuum container 531 a. The exhaust pipe 531 c is connected to the ejector 533 and discharges a gas inside the vacuum container 531 a to the ejector 533. A filter 531 d is attached to the exhaust pipe 531 c to prevent the material from being suctioned up to the ejector 533. The material sent to the vacuum container 531 a is discharged from the discharge port 531 e and sent to the first switching valve 54. The discharge port 531 e can be opened and closed by a bottom lid 531 f rotated by an actuator 531 g. During transport of the material, the material can be transported with more efficiency by closing the discharge port 531 e and sealing the vacuum container 531 a. It is preferable to provide a seal member such as a gasket on an abutting surface of the bottom lid 531 f.

The ejector 533 is a device that generates negative pressure using the Venturi effect. Specifically, the ejector 533 includes a supply port 533 a, an exhaust port 533 b, and an intake port 533 c. The supply port 533 a is connected to a compressed fluid source 25 such as an air compressor via a coupler 623 and thus a compressed fluid is sent to the supply port 533 a. The exhaust port 533 b discharges the compressed fluid sent to the supply port 533 a and the gas inside the vacuum container 531 a suctioned from the intake port 533 c to the outside of the apparatus. The intake port 533 c is connected to a pipeline connecting the supply port 533 a and the exhaust port 533 b and the exhaust pipe 531 c of the vacuum conveyor 531, and suctions the gas inside the vacuum container 531 a using negative pressure generated in the ejector 533.

The configuration of the transporter 53 described above is merely an example, and another configuration may be employed as long as it is of a device that can transport the collected material to the highest level of the conveyance route of the material. Negative pressure may be generated using, for example, a vacuum pump, instead of the ejector 533.

Further, when the material inside the chamber 11 is collected using the material supply unit 5, the material is transported together with the inert gas filling inside the chamber 11. Thus, it is desirable to increase the amount of the inert gas supplied to the chamber 11 when the material is collected to prevent the oxygen concentration inside the chamber 11 from becoming lower because of the collection of the material. In the present embodiment, the inert gas supplier 21 can switch the amount of the inert gas supplied and thus the flow rate of the inert gas supplied to the chamber 11 while the transporter 53 operates can be increased. Specifically, the inert gas supplier 21 supplies the nitrogen gas at a rate of 50 L/min in normal times, and supplies the nitrogen gas at a rate of 80 L/min during an operation of the transporter 53.

Preferably, the first switching valve 54 is provided between the transporter 53 and the sieve 55. The first switching valve 54 selectively switches a discharge destination of the material fed from the transporter 53 to any one of the sieve 55 and the material tank 52 as needed. In the present embodiment, the first switching valve 54 can be electrically controlled and switch the discharge destination of the material according to an instruction from the controller 7.

The sieve 55 may be provided below the transporter 53 and above the chamber 11. In the present embodiment, the sieve 55 is provided between the first switching valve 54 and the second switching valve 56. The sieve 55 of the present embodiment is specifically an ultrasonic sieve, and includes a filter case 551, a mesh filter 553, and a vibration element 555, as illustrated in FIGS. 10 and 11. The filter case 551 holds the mesh filter 553. The mesh filter 553 sorts the material fed from above, removes impurities therefrom, and discharges the material downward. The mesh filter 553 is vibrated at a predetermined frequency with the vibration element 555. Since the mesh filter 553 is vibrated, clogging is less likely to occur and powder can be sorted over a long time. Further, the mesh filter 553 is disposed to incline downward from an upstream side of the material, that is, a feeding side of the material, toward a downstream side of the material, that is, a discharging side of the material. With this configuration, it is possible to prevent the impurities removed by the mesh filter 553 from continuously remaining on the mesh filter 553, and then the impurities are sent at any time to the downstream side. The mesh filter 553 is set to an appropriate angle according to the length of the portion used for sieving. The inclination angle of the mesh filter 553 in the present embodiment is any angle from one degree to three degrees with respect to a horizontal direction. The impurities that have fallen from an end of the mesh filter 553 on the downstream side are discharged from the sieve 55 and sent to a collection container 557. The configuration of the sieve 55 described above is merely an example, and any device may be used as long as it is a device that can remove the impurities. For example, a three-dimensional sieve may be used as the sieve 55.

Preferably, the second switching valve 56 is provided between the sieve 55 and the chamber 11. The second switching valve 56 selectively switches a discharge destination of the material fed from the sieve 55 to any one of the material tank 52 and the chamber 11 as needed. In the present embodiment, the second switching valve 56 can be manually operated, and the operator switches the discharge destination of the material as needed. Alternatively, the second switching valve 56 can be electrically controlled and may switch the discharge destination of the material according to an instruction from the controller 7.

The connection member 57 is provided at an outlet of the material from which the impurities have been removed in the material supply unit 5, that is, between the second switching valve 56 and the chamber 11. As illustrated in FIGS. 12 and 13, the connection member 57 includes a bellows 571, an abutting plate 573, a clamp 575, and a biasing member 577. The bellows 571 is stretchable to enable the material to be flowed, and one end of the bellows 571 is connected to a lower side of the second switching valve 56, and the other end of the bellows 571 is connected to the abutting plate 573. The abutting plate 573 is pressed by the guide member 37 of the additive manufacturing apparatus body 10 to close the conveyance route of the material and prevent the material and the inert gas from leaking. It is preferable to provide a seal member such as a gasket on an abutting surface of the abutting plate 573. The clamp 575 is, for example, a toggle clamp, and fixes the abutting plate 573 in a state of abutting on the guide member 37. The biasing member 577 is, for example, a spring that causes the abutting plate 573 to be separated from the guide member 37 when the clamp 575 is released and contracts the bellows 571. With the connection member 57 described above, the connection of the material supply unit 5 and the additive manufacturing apparatus body 10 at the outlet of the material is easily achieved.

The material supply unit 5 is connected to the other devices via the ferrules 611, 612, and 613, the couplers 621, 622, and 623, the connector 631, and the connection member 57. For this reason, the material supply unit 5 is easily detached from the present additive manufacturing apparatus 1 and further the time required to change the material can be reduced.

According to the material supply unit 5 with the above-described configuration, the collected material is transported to the highest level of the material conveyance route with the one transporter 53, then fed on the sieve 55 by free fall due to gravity and returned to the chamber 11, and thus the apparatus can have a relatively easy configuration and cost can be reduced.

The material fed from the material supply unit 5 passes through the guide member 37 so that the recoater head 33 of the material layer former 3 is replenished with the material. As illustrated in FIGS. 2 and 14, the guide member 37 is inserted into an opening 11 e formed in a top plate 11 d of the replenish chamber 11 c and fixed to the top plate 11 d of the replenish chamber 11 c to be detachable. More specifically, in the present embodiment, the guide member 37 is fixed to the top plate 11 d of the replenish chamber 11 c of the chamber 11 between the molding region R and the discharge opening 311. In other words, the recoater head 33 is replenished with the material in the replenish chamber 11 c located between the molding region R and the discharge opening 311. The guide member 37 is removed from the chamber 11 such as during cleaning when the material is changed. In order to make it easier to detach the guide member 37, the guide member 37 is desirably provided at a relatively low position. For this reason, the top plate 11 d of the replenish chamber 11 c is provided at a position lower than the top plate 11 b of the molding chamber 11 a.

The guide member 37 includes an upper plate 370, a feed chute 371, a shaft 373, a rotary actuator 375, and wipers 377 as illustrated in FIGS. 12 and 13.

The upper plate 370 is provided at an upper end of the feed chute 371 and is larger than the opening 11 e. The upper plate 370 is locked to the top plate 11 d to position the guide member 37 at the upper part of the replenish chamber 11 c. The upper plate 370 is provided with handles 370 a to be easily carried. The upper plate 370 is fixed to the top plate 11 d with fixing members 370 b such as knob screws.

The feed chute 371 is open upward and downward to enable material to be flowed. The feed chute 371 guides the material fed from an outside of the chamber 11, specifically, from the connection member 57 of the material supply unit 5 to the material container 331 of the recoater head 33. The feed chute 371 extends in the horizontal direction along the material supply port 333 of the recoater head 33.

The shaft 373 is provided to be fixed to the feed chute 371 with a mounting member to shut a lower end portion of the feed chute 371. The shaft 373 extends in the horizontal direction and has through holes 374 formed in a direction orthogonal to an axis of the shaft 373, as illustrated in FIG. 15. Discharge of the material is switched to an on- or off-state according to a rotation of the shaft 373 by the rotary actuator 375. FIG. 16 illustrates the state when the material is supplied, in which the shaft 373 is rotated to make the through holes 374 face in a vertical direction and the material is discharged to the recoater head 33. When replenishment of the recoater head 33 with the material is completed, the through holes 374 is shut by the stored material, which automatically stops discharge of the material. Then, the shaft 373 is rotated to make the through holes 374 face in a horizontal direction, and the lower end portion of the feed chute 371 is closed, as illustrated in FIG. 17.

The wipers 377 are provided at the lower end portion of the feed chute 371 to be in slidable contact with the shaft 373. In the present embodiment, a pair of wipers 377 are provided to interpose the shaft 373 therebetween as illustrated in FIGS. 16 and 17. The wipers 377 prevent the material from leaking from a gap between the feed chute 371 and the shaft 373.

By feeding the material to the recoater head 33 via the guide member 37 as described above, the amount of the material stored in the recoater head 33 can be kept at a certain degree when the recoater head 33 is replenished with the material. In addition, because the shaft 373 and the rotary actuator 375 are used as a discharge switching mechanism that switches the discharge of the material to the on- or off-state, the material is less likely to be jammed therein when the discharge of the material is switched to the on- or off-state. In addition, because the material can be fed from a position close to the recoater head 33, it is possible to suppress flying up of the material. Particularly, because the discharge switching mechanism that switches the discharge of the material to the on- or off-state is configured with the shaft 373 and the rotary actuator 375, the guide member 37 can be configured in a relatively small size. However, another discharge switching mechanism such as an openable and closeable shutter may be used.

Particularly, the guide member 37 of the present embodiment is effective especially when it is desired to set the amount of the material contained in the recoater head 33 to be small. If a large amount of the material is stored in the recoater head 33, the discharge amount of the material becomes unstable because of the weight of the material. In addition, if a large amount of the material is stored in the recoater head 33, clogging by the material is more likely to occur. For this reason, it is desirable to set the amount of the material contained in the recoater head 33 to be small. In the present embodiment, a sufficient amount of the material for forming one material layer 83 is supplied from the guide member 37 to the recoater head 33 each time one material layer 83 is formed. The amount of the material stored in the recoater head 33 immediately after replenishment with the material, that is, the maximum amount of the material stored in the recoater head 33, is, for example, equal to or greater than an amount necessary for forming one material layer 83 and less than an amount necessary for forming two material layers 83.

Each part of the additive manufacturing apparatus 1 is provided with an oximeter. For example, a chamber oximeter 661 connected to the chamber 11 and a fume collector oximeter 662 connected to the fume collector 23 are provided. In the present embodiment, a material supply unit oximeter 663 connected to the material supply unit 5 is further provided. Providing the material supply unit oximeter 663 is effective especially when a highly flammable material such as aluminum or titanium is used. The material supply unit oximeter 663 is desirably provided on a relatively downstream of the material conveyance route in the material supply unit 5, and specifically, is connected to the filter case 551 of the sieve 55 in the present embodiment. Because it is estimated that an oxygen concentration on the upstream of a detection position is lower than an oxygen concentration at the detection position, the material supply unit oximeter 663 is connected to the sieve 55 disposed on a relatively downstream on the material conveyance route. The positions and the number of oximeters described above are examples, and any oximeters may be provided in a range in which an oxygen concentration can be detected within the additive manufacturing apparatus 1. For example, only the chamber oximeter 661 may be provided, or only the chamber oximeter 661 and the material supply unit oximeter 663 may be provided.

The controller 7 controls each part and performs control of additive manufacturing including a material replenishing operation and a material collecting operation. Particularly in the present embodiment, the controller 7 controls each part based on the oxygen concentration value detected by each oximeter. Specifically, when an oxygen concentration detected by the oximeter is greater than a predetermined threshold, the controller 7 stops the irradiation device 4 not to form the solidified layer 85 until the oxygen concentration becomes the predetermined threshold or less again. In addition, when an oxygen concentration detected by the oximeter is greater than the predetermined threshold, the controller 7 stops the material supply unit 5 not to collect the material until the oxygen concentration becomes the predetermined threshold or less again. In a case in which a plurality of oximeters is provided and at least one oximeter measures an oxygen concentration exceeding the predetermined threshold, collecting the material is avoided. In other words, the transporter 53 of the material supply unit 5 of the present embodiment is configured to operate only when the oxygen concentrations of the inside of the chamber 11, the inside of the fume collector 23, and the material supply unit 5 are the predetermined threshold or less. In the present embodiment, the threshold of the oxygen concentration is, for example, 3%. With the above-described control, the material can be prevented from being degraded and molded more safely. The controller 7 may be configured by optionally combining hardware and software, and includes, for example, a CPU, a RAM, a ROM, an auxiliary storage device, and an input/output interface.

Each part of the additive manufacturing apparatus 1 is desirably provided with a material sensor that detects the presence or absence of the material. Specifically, in the present embodiment, a material sensor 671 is provided for the recoater head 33, a material sensor 672 is provided for the guide member 37, a material sensor 673 is provided for the first discharge chute 16, a material sensor 674 is provided for the second discharge chute 17, material sensors 675 and 676 are provided for the material tank 52, and a material sensor 677 is provided for the collection container 557. Each of the material sensors 671, 672, 673, 674, 675, 676, and 677 is electrically connected to the controller 7, and sends detection signals indicating detection results to the controller 7. The material sensor 671 detects whether a sufficient amount of the material is stored in the material container 331 of the recoater head 33. The material sensor 672 detects whether a sufficient amount of the material is stored in the feed chute 371 of the guide member 37. The material sensor 673 detects whether a sufficient amount of the material is stored in the first discharge chute 16. The material sensor 674 detects whether a sufficient amount of the material is stored in the second discharge chute 17. The material sensors 675 and 676 are provided an upper part and a lower part of the material tank 52, respectively. When the material sensor 675 detects that the material is above an upper limit position of the material tank 52, a warning is displayed on the display device 73. When the material sensor 676 detects that the material is below a lower limit position of the material tank 52, a warning is displayed on the display device 73. The material sensor 677 is provided at an upper part of the collection container 557. When the material sensor 677 detects that the material is above an upper limit position of the collection container 557, a warning is displayed on the display device 73.

Here, an additive manufacturing method performed using the above-described additive manufacturing apparatus 1 will be described. First, the base plate 81 is placed on the molding table 14, and the inside of the chamber 11 is filled with the inert gas at the predetermined concentration. Then, the height of the molding table 14 is adjusted to a proper position. In this state, the recoater head 33 moves on the molding region R and discharges material on the molding region R. The material is leveled by the blades 35 and thereby the first material layer 83 is formed on the base plate 81. The recoater head 33 moves to the replenish chamber 11 c to receive replenishment of the material from the material supply unit 5 via the guide member 37. Next, the irradiation device 4 irradiates an irradiation region of the first material layer 83 with the laser beam L. The laser beam L sinters or melts the material within the irradiation region to form a first solidified layer 85. Then, the molding table 14 is lowered as much as the thickness of the material layer 83, the recoater head 33 is moved on the molding region R to form a second material layer 83 on the first solidified layer 85. The recoater head 33 moves to the replenish chamber 11 c to receive replenishment with the material from the material supply unit 5 via the guide member 37. The irradiation device 4 irradiates the second material layer 83 with the laser beam L to form a second solidified layer 85. Third and thereafter material layers 83 and solidified layers 85 are formed by repeating the same procedures, a plurality of solidified layers 85 is laminated, and thereby the desired three-dimensional molded object is formed. Further, the replenishment of the recoater head 33 with the material and the formation of the solidified layers 85 may be performed in parallel.

Here, an example of the material replenishing operation during additive manufacturing will be described in detail with reference to FIG. 18. Each time a predetermined number of material layers 83 is formed, i.e., each time one material layer 83 is formed in the present embodiment, the recoater head 33 is moved to the replenish chamber 11 c, and the material replenishing operation with respect to the material container 331 of the recoater head 33 is started. Further, it may be configured that the material replenishing operation is started when the material sensor 671 detects that a predetermined amount of the material or less is present in the material container 331. In addition, even in a configuration in which the material replenishing operation is performed each time a predetermined number of material layers 83 are formed, when the material sensor 671 detects that a predetermined amount of the material or less is present in the material container 331 during the formation of the material layers 83, the formation of the material layers 83 may be stopped, and the formation of the material layers 83 may be performed again after the material replenishing operation is performed. Further, the material discharge destination of the first switching valve 54 is set to the sieve 55, and the material discharge destination of the second switching valve 56 is set to the chamber 11.

First, the shaft 373 of the guide member 37 is rotated, and the material stored in the feed chute 371 is fed to the recoater head 33 (S11). If the material sensor 671 detects that the recoater head 33 has been replenished with a sufficient amount of the material (No in S12), the material replenishing operation ends, and the formation of the material layer 83 and the solidified layer 85 is resumed. If the material sensor 672 detects that the material inside the feed chute 371 has been substantially consumed and thus the material inside the recoater head 33 is insufficient (Yes in S12), an operation to collect the excess material in the chamber 11 and replenish the recoater head 33 is performed.

First, the oxygen concentrations inside the additive manufacturing apparatus 1 are measured by the chamber oximeter 661, the fume collector oximeter 662, and the material supply unit oximeter 663, and whether the oxygen concentrations are equal to or less than a predetermined threshold is determined (S13). If the oxygen concentrations exceed the predetermined threshold, the additive manufacturing apparatus waits until the concentrations are equal to or less than the threshold (S14).

Next, the material sensor 673 checks whether the material is stored in the first discharge chute 16, and if there is the material in the first discharge chute (Yes in S15), the material is supplied from the first discharge chute 16 (S16). Specifically, with the valve 642 opened and the valves 641, 643, and 644 closed, the compressed fluid is supplied from the compressed fluid source 25 to the ejector 533 of the transporter 53. At this time, it is desirable to increase the amount of the inert gas supplied from the inert gas supplier 21. The material suctioned up by the transporter 53 passes through the first switching valve 54, the sieve 55, the second switching valve 56, and the connection member 57, and falls to the guide member 37. The material is supplied from the guide member 37 again (S11), and if the recoater head 33 is replenished with a sufficient amount of the material (No in S12), the material replenishing operation ends. If the amount of material in the recoater head 33 is still insufficient even after the material is supplied from the first discharge chute 16 (Yes in S12) or if there is not a sufficient amount of material in the first discharge chute 16 (No in S15), the material is supplied from the second discharge chute 17.

After whether the oxygen concentrations inside the additive manufacturing apparatus 1 are equal to or less than the predetermined threshold is determined as described above, the material sensor 674 determines whether the material is stored in the second discharge chute 17, and if there is the material in the second discharge chute (Yes in S17), the material is supplied from the second discharge chute 17 (S18). Specifically, with the valve 643 opened and the valves 641, 642, and 644 closed, the compressed fluid is supplied from the compressed fluid source 25 to the ejector 533 of the transporter 53. At this time, it is desirable to increase the amount of the inert gas supplied from the inert gas supplier 21. The material suctioned up by the transporter 53 passes through the first switching valve 54, the sieve 55, the second switching valve 56, and the connection member 57, and falls to the guide member 37. The material is supplied from the guide member 37 again (S11), and if the recoater head 33 is replenished with a sufficient amount of the material (No in S12), the material replenishing operation ends. If the amount of material in the recoater head 33 is still insufficient even after the material is supplied from the second discharge chute 17 (Yes in S12) or if there is not a sufficient amount of the material in the second discharge chute 17 (No in S17), the material is supplied from the material tank 52.

After it is determined whether the oxygen concentrations inside the additive manufacturing apparatus 1 are equal to or less than the predetermined threshold as described above, the material is supplied from the material tank 52 (S19). Specifically, with the valve 641 opened and the valves 642, 643, and 644 closed, the compressed fluid is supplied from the compressed fluid source 25 to the ejector 533 of the transporter 53. At this time, it is desirable to increase the amount of the inert gas supplied from the inert gas supplier 21. The material suctioned up by the transporter 53 passes through the first switching valve 54, the sieve 55, the second switching valve 56, and the connection member 57, and falls to the guide member 37. The material is supplied from the guide member 37 again (S11), and if the recoater head 33 is replenished with a sufficient amount of the material (No in S12), the material replenishing operation ends.

As described above, the material is collected from the chamber 11 via the first discharge chute 16 and the second discharge chute 17 during the additive manufacturing, and the collected material or the material stored in the material tank 52 is sieved every time and supplied to the recoater head 33.

Here, an example of the material collecting operation after additive manufacturing will be described in detail with reference to FIG. 19. The material discharge destination of the first switching valve 54 is set to the material tank 52. In addition, it is desirable to maintain the oxygen concentrations inside the additive manufacturing apparatus 1 at the predetermined threshold or lower during the material collecting operation as well.

First, the recoater head 33 is moved to above the discharge opening 311 or the discharge opening 313, and the material inside the material container 331 is discharged to the first discharge chute 16 or the second discharge chute 17 (S21). Next, the material is collected from the first discharge chute 16 (S22). Specifically, with the valve 642 open and the valves 641, 643, and 644 closed, the compressed fluid is supplied from the compressed fluid source 25 to the ejector 533 of the transporter 53. The material inside the first discharge chute 16 is suctioned up by the transporter 53, passes through the first switching valve 54, and is sent to the material tank 52. Next, the material is collected from the second discharge chute 17 (S23). Specifically, with the valve 643 opened and the valves 641, 642, and 644 closed, the compressed fluid is supplied from the compressed fluid source 25 to the ejector 533 of the transporter 53. The material of the second discharge chute 17 is suctioned up by the transporter 53, passes through the first switching valve 54, and is sent to the material tank 52. Then, the material is collected from the suction nozzle 18 (S24). Specifically, the operator moves the suction nozzle 18 to a desired position inside the chamber 11 through the glove box. With the valve 644 opened and the valves 641, 642, and 643 closed in that state, the compressed fluid is supplied from the compressed fluid source 25 to the ejector 533 of the transporter 53. The material is suctioned up from the suction nozzle 18 by the transporter 53, passes through the first switching valve 54, and is sent to the material tank 52.

As described above, the material is collected from the chamber 11 via the first discharge chute 16, the second discharge chute 17, and the suction nozzle 18 after additive manufacturing. Because an amount of the material collected after additive manufacturing is generally large, it takes quite a time to remove the impurities from the material using the sieve 55. Thus, in the present embodiment, the collected material is sent directly to the material tank 52 without sieving it. In the material supply unit 5 of the present embodiment, the sieve 55 is disposed on a downstream side of the conveyance route from the material tank 52. For this reason, even if the material mixed with the impurities is discharged from the material tank 52 during additive manufacturing, the material is sent to the recoater head 33 after removing the impurities. However, the material discharge destination of the first switching valve 54 may be set to the sieve 55, the material discharge destination of the second switching valve 56 may be set to the material tank 52, and the collected material may be sieved and then sent to the material tank 52.

The material replenishing operation and the material collecting operation described above are merely examples, and the orders of the steps may be changed, or the flow path may be appropriately switched as needed. In addition, the material may be transported after the material discharge destination of the first switching valve 54 is set to the sieve 55 and the material discharge destination of the second switching valve 56 is set to the material tank 52, and the material discharged from the second switching valve 56 may be returned to a material bottle manually by removing the ferrule 614 connecting the second switching valve 56 and the material tank 52.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure covers modifications and variations provided that they fall within the scope of the following claims and their equivalents. 

What is claimed is:
 1. An additive manufacturing apparatus comprising: a chamber; a material layer former provided in the chamber and configured to form a material layer with a predetermined thickness; an inert gas supplier configured to supply an inert gas at a predetermined concentration to the chamber; and a material supply unit configured to collect material discharged from the chamber and replenish the material layer former with the material, wherein the material supply unit comprises a material tank configured to store the material, a transporter configured to transport the material discharged from the chamber and the material tank to a highest level on a conveyance route of the material, and a sieve provided below the transporter and above the chamber, and configured to remove impurities from the material sent from the transporter and discharge the material downward to replenish the material layer former with the material.
 2. The additive manufacturing apparatus according to claim 1, wherein the material supply unit further comprises a cabinet configured to be movable, and wherein the cabinet houses the material tank, the transporter, and the sieve.
 3. The additive manufacturing apparatus according to claim 1, wherein the material layer former comprises a base having a molding region in which a desired three-dimensional molded object is formed, a recoater head that moves on the base in a horizontal direction, and a blade attached to the recoater head to level the material to form the material layer, and wherein the recoater head comprises a material container that stores the material, a material supply port that is provided on an upper surface of the material container and serves as a reception port of the material supplied to the material container, and a material discharge port that is provided at a bottom of the material container and discharges the material to the molding region.
 4. The additive manufacturing apparatus according to claim 1, further comprising: a guide member that is provided on the chamber and configured to guide the material discharged from the material supply unit to the material layer former.
 5. The additive manufacturing apparatus according to claim 4, wherein the guide member comprises a feed chute that is open upward and downward and configured to enable the material to be flowed, a shaft that is provided to shut a lower end portion of the feed chute, extends in a horizontal direction, and has a through hole formed in a direction orthogonal to an axis, and a rotary actuator that rotates the shaft, wherein discharge of the material from the guide member is switched to an on- or off-state by rotating the shaft.
 6. The additive manufacturing apparatus according to claim 4, wherein the material supply unit further comprises a connection member that is provided at an outlet of the material to the chamber in the material supply unit, and wherein the connection member comprises a bellows that is able to stretch and enables the material to be flowed, an abutting plate that is connected to a lower end of the bellows and pressed by the guide member, and a clamp that fixes the abutting plate in a state of abutting on the guide member.
 7. The additive manufacturing apparatus according to claim 1, wherein the inert gas supplier is configured to enable an amount of the inert gas supplied to be switched and a flow rate of the inert gas supplied to the chamber while the transporter operates to be increased.
 8. The additive manufacturing apparatus according to claim 1, wherein the inert gas supplier supplies the inert gas also to the material tank.
 9. The additive manufacturing apparatus according to claim 1, further comprising: a first bypass that is connected to the chamber and the material tank and enables the inert gas to be flowed; and a second bypass that is connected to the material tank and a pipe between the material tank and the transporter and enables the inert gas to be flowed.
 10. The additive manufacturing apparatus according to claim 1, wherein the transporter comprises a vacuum conveyor and an ejector, wherein the vacuum conveyor comprises a vacuum container, a supply pipe that is provided on the vacuum container and connected to the chamber and the material tank, an exhaust pipe that is provided on the vacuum container and discharges a gas inside the vacuum container, a discharge port that is formed at a lower end of the vacuum container that discharges the material, and a bottom lid that opens and closes the discharge port, and wherein the ejector comprises a supply port for supplying a compressed fluid, an exhaust port for emitting the compressed fluid and the gas inside the vacuum container, and an intake port that is connected to a pipeline connecting the supply port and the exhaust port and the exhaust pipe.
 11. The additive manufacturing apparatus according to claim 1, further comprising: a first switching valve that is provided between the transporter and the sieve and switches a discharge destination of the material to any one of the sieve and the material tank.
 12. The additive manufacturing apparatus according to claim 1, wherein the sieve comprises a mesh filter that sorts the material and a vibration element that vibrates the mesh filter.
 13. The additive manufacturing apparatus according to claim 12, wherein the mesh filter inclines downward from an upstream side to a downstream side of the material.
 14. The additive manufacturing apparatus according to claim 1, further comprising: a second switching valve that is provided between the sieve and the chamber and switches a discharge destination of the material to any one of the chamber and the material tank.
 15. The additive manufacturing apparatus according to claim 1, further comprising: a chamber oximeter that is connected to the chamber and measures an oxygen concentration inside the chamber, wherein the transporter operates only when the oxygen concentration inside the chamber is equal to or less than a predetermined threshold.
 16. The additive manufacturing apparatus according to claim 15, further comprising: a material supply unit oximeter that is connected to the material supply unit and measures an oxygen concentration inside the material supply unit, wherein the transporter operates only when the oxygen concentration inside the chamber and the oxygen concentration inside the material supply unit are equal to or less than the predetermined threshold.
 17. The additive manufacturing apparatus according to claim 16, wherein the material supply unit oximeter is connected to the sieve. 